This invention relates to polyvinyl chloride (PVC) dispersion and blending resin compositions and to preparation and use of such compositions in the production of whitened PVC foam.
Polyvinyl chloride (PVC) foam processes often require a high degree of whiteness in the finished foam product without sacrificing process performance properties such as activation levels, cell structure, overblow protection and the like. The PVC resin used in the process is one of the ingredients primarily responsible for these performance characteristics. Previously, it has been attempted to control the desired characteristics by the use of additives, such as blowing agents, activators, pigments such as titanium dioxide and the like.
It is clearly desirable to achieve the improved whiteness without the use of or with the use of reduced quantities of these added materials.
According to the present invention a whitened PVC chloride foam is produced by incorporating in a plastisol containing dry, particulate PVC dispersion resin;
(i) from about 0.01 to about 5 parts by weight per 100 parts by weight of dry, particulate polyvinyl chloride dispersion resin of at least one additive selected from the group consisting of:
a) a sulfonic acid derivative having the formula Rxe2x80x94SO3M wherein R is an alkyl, alkylaryl or an arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl and the like and wherein M is selected from hydrogen and monovalent metals;
b) a sulfinic acid derivative having the formula Rxe2x80x94SO2M wherein R is an alkyl, alkylaryl or an arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl or the like and wherein M is selected from hydrogen and monovalent metals; and
c) mercapto acetic acid sodium salt; and,
(ii) optionally incorporating at least one second additive selected from the group consisting of
a) at least one water soluble metal salt selected from the group consisting of water soluble salts of alkali metals, alkaline-earth metals and transition metals; and
b) t-butyl hydroperoxide; and heating the plastisol to effect expansion into whitened PVC foam.
The invention further comprises a method of producing whitened PVC chloride foam by incorporating in a plastisol containing dry, particulate PVC dispersion resin and dry, particulate PVC blending resin;
(i) from about 0.01 to about 5 parts by weight per 100 parts by weight of dry, particulate polyvinyl chloride blending resin of at least one additive selected from the group consisting of:
a) a sulfonic acid derivative having the formula Rxe2x80x94SO3M wherein R is an alkyl, alkylaryl or an arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl and the like and wherein M is selected from hydrogen and monovalent metals;
b) a sulfinic acid derivative having the formula Rxe2x80x94SO2M wherein R is an alkyl, alkylaryl or an arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl or the like and wherein M is selected from hydrogen and monovalent metals; and
c) mercapto acetic acid sodium salt; and,
(ii) optionally incorporating at least one second additive selected from the group consisting of
a) at least one water soluble metal salt selected from the group consisting of water soluble salts of alkali metals, alkaline-earth metals and transition metals; and
b) t-butyl hydroperoxide; and heating the plastisol to effect expansion into whitened PVC foam.
The invention further comprises a dry, particulate PVC dispersion resin for use in the production of whitened PVC foam comprising vinyl chloride polymer and;
(i) from about 0.01 to about 5 parts by weight per 100 parts by weight of dry, particulate PVC dispersion resin of at least one additive selected from the group consisting of:
a) a sulfonic acid derivative having the formula Rxe2x80x94SO3M wherein R is an alkyl, alkylaryl or an arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl or the like and wherein M is selected from hydrogen and monovalent metals;
b) a sulfinic acid derivative having the formula Rxe2x80x94SO2M wherein R is an alkyl, alkylaryl or an arylalkyl group consisting from 1 to 12 carbon atoms which may also contain other functional groups such as hydroxyl, carboxyl and the like and wherein M is selected from the group consisting of hydrogen and monovalent metals;
c) mercapto acetic acid sodium salt; and,
(ii) optionally containing at least one second additive selected from the group consisting of:
a) a water soluble metal salt selected from the group consisting of water soluble salts of mono- and divalent alkali metals, alkaline-earth metals and transition metals; and
b) t-butyl hydroperoxide.
The invention further comprises a dry, particulate PVC blending resin for use in a plastisol containing dry, particulate PVC dispersion resin and dry particulate PVC blending resin for the production of whitened PVC foam, said dry, particulate PVC blending resin comprising vinyl chloride polymer and;
(i) from about 0.01 to about 5 parts by weight per 100 parts by weight of dry, particulate PVC blending resin of at least one additive selected from the group consisting of:
a) a sulfonic acid derivative having the formula Rxe2x80x94SO3M wherein R is an alkyl, alkylaryl or an arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl or the like and wherein M is selected from hydrogen and monovalent metals;
b) a sulfinic acid derivative having the formula Rxe2x80x94SO2M wherein R is an alkyl, alkylaryl or an arylalkyl group consisting from 1 to 12 carbon atoms which may also contain other functional groups such as hydroxyl, carboxyl and the like and wherein M is selected from the group consisting of hydrogen and monovalent metals;
c) mercapto acetic acid sodium salt; and,
(ii) optionally cocomprising at least one second additive selected from the group consisting of:
a) at least one water soluble metal salt selected from the group consisting of water soluble salts of alkali metals, alkaline-earth metals and transition metals; and
b) t-butyl hydroperoxide.
The invention further comprises a PVC plastisol for use in the production of a whitened PVC foam comprising dry, particulate PVC dispersion resin and from;
(i) about 0.01 to about 5 parts by weight per 100 parts by weight of dry, particulate PVC dispersion resin of at least one additive selected from the group consisting of:
a) a sulfonic acid derivative having the formula Rxe2x80x94SO3M wherein R is an alkyl, alkylaryl or an arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl or the like and wherein M is selected from hydrogen and monovalent metals;
b) a sulfinic acid derivative having the formula Rxe2x80x94SO2M wherein R is an alkyl, alkylaryl or an arylalkyl group consisting from 1 to 12 carbon atoms which may also contain other functional groups such as hydroxyl, carboxyl and the like and wherein M is selected from the group consisting of hydrogen and monovalent metals;
c) mercapto acetic acid sodium salt; and,
(ii) optionally comprising at least one second additive selected from the group consisting of:
a) at least one water soluble metal salt selected from the group consisting of water soluble salts of alkali metals, alkaline-earth metals and transition metals; and
b) t-butyl hydroperoxide.
The invention further comprises a whitened PVC foam produced by heating a plastisol comprising a dry, particulate PVC dispersion resin and;
(i) from about 0.01 to about 5 parts by weight per 100 parts by weight of dry, particulate PVC dispersion resin of at least one additive selected from the group consisting of:
a) a sulfonic acid derivative having the formula Rxe2x80x94SO3M wherein R is an alkyl, alkylaryl or an arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl or the like and wherein M is selected from hydrogen and monovalent metals;
b) a sulfinic acid derivative having the formula Rxe2x80x94SO2M wherein R is an alkyl, alkylaryl or an arylalkyl group consisting from 1 to 12 carbon atoms which may also contain other functional groups such as hydroxyl, carboxyl and the like and wherein M is selected from the group consisting of hydrogen and monovalent metals;
c) mercapto acetic acid sodium salt; and,
(ii) optionally comprising at least one second additive selected from the group consisting of:
a) at least one water soluble metal salt selected from the group consisting of water soluble salts of alkali metals, alkaline-earth metals and transition metals; and
b) t-butyl hydroperoxide.
According to the present invention, improved foam characteristics of a PVC foam can be achieved by adding at least one sulfur compound selected from sulfonic acid derivatives, sulfinic acid derivatives, and mercapto acetic acid sodium salt, and optionally adding at least one of a water soluble metal salt and t-butyl hydroperoxide, directly or indirectly, to at least one of a PVC dispersion resin polymerization recipe or latex, or to a PVC blending resin polymerization recipe or slurry, or to a PVC plastisol containing a PVC dispersion resin and optionally containing a PVC blending resin and heating the plastisol to produce a whitened foam. The term xe2x80x9cdispersion resinxe2x80x9d is used to describe any PVC resin that is made by an emulsion, microsuspension or HYBRID process primarily for use in the production of PVC plastisols. HYBRID is a registered trademark of Occidental Chemical Corporation for its PVC dispersion resin polymerization process. Typically the plastisol is heated to a temperature from about 180 to about 210xc2x0 C. for a time from about 0.75 to about 1.75 minutes.
Typically the plastisol contains from about 15 to about 75 weight percent of the PVC dispersion resin based upon the total weight of the plastisol constituents. The PVC dispersion resin comprises PVC resin particles having an average particle diameter from about 0.1 to about 10 microns. The plastisol may also contain PVC blending resin. Typically the PVC blending resin comprises PVC resin particles having an average particle diameter from about 20 to about 40 microns and is present in the plastisol in an amount up to about 50 weight percent of the dry PVC resin in the plastisol.
According to the present invention, the sulfur compounds are used alone or in combination with water soluble metal salts and/or t-butyl hydroperoxide. The sulfur compounds are selected from the group consisting of sulfonic acid derivatives, sulfinic acid derivatives, and mercapto acetic acid sodium salt. The sulfonic acid derivatives generally have the formula Rxe2x80x94SO3M wherein R is an alkyl, alkylaryl or arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl, or the like and wherein M is selected from hydrogen and monovalent metals. Preferably M is selected from hydrogen, sodium and potassium.
The sulfinic acid derivatives generally have the formula Rxe2x80x94SO2M, wherein R is an alkyl, alkylaryl or arylalkyl group containing from 1 to 12 carbon atoms which may also contain one or more other functional groups such as hydroxyl, carboxyl, or the like and wherein M is selected from the group consisting of hydrogen and monovalent metals. Preferably M is selected from hydrogen, sodium, and potassium.
Mercapto acetic acid sodium salts are also effective.
These sulfur compounds are effective whiteners when used alone according to the present invention. These sulfur compounds may be added to a polymerization recipe for the production of a PVC dispersion resin or a PVC blending resin, or they may be added as a post additive to polymerized latex in the production of the PVC dispersion resin or slurry in the production of the PVC blending resin. The sulfur compounds may also be added to the plastisol. In each instance, it is necessary that the sulfur compounds be relatively uniformly distributed throughout the material. The sulfur compounds are added in an amount equal to from about 0.01 to about 5 parts by weight per hundred parts by weight of dry PVC dispersion resin in the plastisol used for the production of the PVC foam. The best results are obtained in the 0.05 to 0.5 parts per hundred parts of dry PVC dispersion resin range. This is dependent on the amount of PVC dispersion resin used in the plastisol. Addition of these sulfur compounds at this level increases the whiteness of the PVC foam produced from the plastisol.
The preferred sulfur compounds are sodium methane sulfoxylate, sodium formaldehyde sulfoxylate, sodium formaldehyde bisulfite, sodium toluene sulfoxylate, sodium acetone bisulfite, sodium methane bisulfite, and mercapto acetic acid sodium salt.
Of these, sodium methane sulfonate and sodium formaldehyde sulfoxylate are preferred.
The at least one water soluble metal salt is generally a water soluble salt of a mono- or divalent alkali metal, alkaline-earth metal or transition metal. Preferably the metal is sodium, potassium, calcium, zinc, tin, nickel or cobalt. Typically, the salt is a chloride, chlorate, hydroxide, nitrate, borate, iodate, thiosulfate or sulfate, although other salts may be used as well, provided they have the desired solubility. The term xe2x80x9cwater soluble saltsxe2x80x9d refers to the ability of the salt to dissolve in the aqueous PVC dispersion in which it is used.
The metal salts and/or t-butyl hydroperoxide may be added to a polymerization recipe for the production of a PVC dispersion resin or a PVC blending resin, or they may be added as a post additive to polymerized latex in the production of the PVC dispersion resin or slurry in the production of the PVC blending resin. The metal ions may also be added to the plastisol in an oil soluble form. In each instance, it is necessary that the salts be relatively uniformly distributed throughout the material. Typically, the metal salts and/or the t-butyl hydroperoxide are added in an amount at least about 0.001 parts by weight per 100 parts by weight of dry PVC dispersion resin in the plastisol. Preferably, the metal salts and/or the t-butyl hydroperoxide are added in an amount of from about 0.01 to about 0.1 parts by weight of dry PVC dispersion resin in the plastisol.
The use of metal salts, when used alone, is effective to reduce the activation temperature during the foam curing process. The use of at least one of the metal salts and the sulfur compounds in combination is effective to synergistically improve the color and reduce the activation temperature required in the production of the PVC foam.
Use of metal salts alone shows noticeable improvement in foam activation temperature and use of the sulfur compounds alone shows noticeable improvement in foam whiteness. This improvement in the color and activation temperature will allow formulators to use lower levels of known additives, such as blowing agent, activator and titanium oxide. The use of such known additives is considered to be well known and need not be discussed further.
Desirably, the sulfur compounds and the metal salts or and/or t-butyl hydroperoxide are used in combination for best results. The use of these additives in combination results in a significant and synergistic improvement in the whiteness level and a reduction in the activation temperature, which is achievable in the production of a PVC foam. In tests of various PVC foam formulations, it was observed that the compositions and method of the present invention are effective to result in improvements in activation temperatures and in whiteness in all instances. While a variety of proprietary PVC formulations were evaluated, the results indicated that the improvement with all formulations was substantially the same. These results were also readily observed using a standard generic foam formula such as:
It will be noted that in the general foam formula, both a PVC dispersion resin and a PVC blending resin are included in the plastisol. It will also be noted that an oil (plasticizer), dioctyl phthalate, is also included. This formulation is representative of standard formulations used to produce the plastisols used for the production of PVC foam.
It is desirable to produce either the PVC dispersion resin or the PVC blending resin to include the desired quantity of the sulfur compounds and water soluble metal salts and/or t-butyl hydroperoxide so that in the plastisol the added materials, i.e., the sulfur compounds and the metal salt or t-butyl hydroperoxide, are present in the plastisol in the ranges discussed above.
The use of the PVC dispersion resin or the PVC blending resin containing the added materials of the present invention to produce a plastisol clearly results in the presence of the desired quantities of added materials in the plastisol. As described below in the examples, the PVC dispersion resin and the PVC blending resin are dried using a spray drying or an equivalent process. The resulting resins may then be mixed into the plastisol foam formulations.
The use of these plastisols then results in the production of a foam, which is whiter and which can be produced at a lower activation temperature than comparable formulations, which do not include the additives of the present invention.
The effectiveness of the present invention is demonstrated in the tests shown below in Example I.